Rabbit Hole for Tuniac is not a SVP, it is a native Tuniac visual but is only compiled in 32bit.
Feldspar could build a 64bit Rabbit Hole for Tuniac, but so far has not.

SVP Renderer is still only compiled and distributed as 32bit only. It does compile fine under 64bit but there is no 64bit SVP's.
Feldspar could compile a 64bit Rabbit Hole SVP, but is highly unlikely to do so

In reality there is no need to be using 64bit Tuniac, you only lose features . You should just install 32bit, the default installer these days is 32bit only.